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            location.href = 'http://www.itcast.cn';  //浏览器跳转页面
        })

        var timer = 5;
        countDown();    //把条件写在一个函数里面，然后首先执行这个函数，防止页面一开始刷白
        setInterval(countDown, 1000);

        function countDown() {
            if (timer == 0) {
                location.href = 'http://www.itcast.cn';  //浏览器跳转页面
            } else {
                div.innerHTML = '你将在' + timer + '秒钟之后跳转到首页';
                timer--;

            }
        }

        // var timer = 5;
        // setInterval(function () {
        //     if (timer == 0) {
        //         location.href = 'http://www.itcast.cn';  //浏览器跳转页面
        //     } else {
        //         div.innerHTML = '你将在' + timer + '秒钟之后跳转到首页';
        //         timer--;

        //     }
        // }, 1000);

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